Muffler with vibration damping shell



Sept. 6 1955 F. E. DEREMER MUFFLER WITH VIBRATION DAMPING SHELL Filed Aug. 28, 1951 INVENTORS TL UYD F. .UEHE'MEH.

BY M ATTORNEY Manufacturing Company, Grand Haven, Mich, a con poration of Michigan Application August 28, 1951, Serial No. 243369 '7 Claims. (Cl. l st-61) This invention relates to apparatus for attenuating sound waves and more especially to the attenuation of sound waves entrained within the exhaust gas streams of an internal combustion engine and to a method of fabricating the sound attenuating apparatus.

The conventional type mother in use at the present time usually consists of a substantially closed chamber or shell having a wall formed of a single sheet of metal to tubular shape having end heads provided with inlet and exhaust passageways at the respective ends of the chamber and is interiorly constructed with gas passages, baffles and sound attenuating compartments. The mufiler may enclose tubular components provided with upwards of hundreds of small openings for attenuating objectionable sound waves entrained in an exhaust gas stream from an internal combustion engine. The sound attenuating components within the muifier are substantially effective in silencing or attenuating most of the objectionable range of sound waves but the exterior wall or shell presents an additional problem in sound attenuation. The chamber wall is subj ct to vibration and certain of the vibrations set up by reason of the high speed of travel of the exhaust gas stream and the pulsations of successive explosions of the engine with which the muffler is used result in a very objectionable rumble or noise by reason of unattenuated waves of comparatively low frequency.

it has been proposed to dampen the vibrations of the shell by lining the same with asbestos or other nonmetallic fibrous material capable of withstanding comparatively high temperatures encountered during muffler operation. However, such linings are expensive and are subject to relatively rapid deterioration, and the vibration of the shell wall by sound waves in the gas stream and that caused by movement of the vehicle tend to reduce the material to a comminuted form and, hence, greatly impair the efliciency of the material to dampen shell noise. After periods of use, the fibrous material may become Wholly ineffective to reduce noise.

The present invention has for an object the provision of means for establishing a plurality of substantially closed compartments or chambers adjacent the shell walls and reinforcing the walls in a manner to substantially eliminate or greatly reduce the shell noise.

Another object of the invention resides in the provision of a sound attenuating muffler or silencer having spaced inner and outer shell walls with an intermediary component or member fashioned to hold the walls in spaced relation and at the same time establish parallel closed chambers and wherein the engagement of spaced portions of the member with the spaced walls serves to reinforce them and modify the vibration period thereof to a frequency which does not result in objectionable audible sounds.

Another object of the invention is the provision of a mufller construction embodying spaced wall plies in combination with an intermediate member formed of metal and specially configurated to engage the-inner and outer walls to retain them in spaced relation and to reinforce nits States Patent resented sent. "5, iii lib and modify their periodicity of vibration to an unobjectionable range so as to minimize shell noise when the device is in use.

Another object of the invention is the provision of a silencer or mufller construction for use with an exhaust gas stream embodying a multi-layer or multi-ply wall construction wherein one of the layers is of undulated configuration and cooperates with another layer to form a plurality of isolated air or gas chambers for effectively reducing the vibration of the shell wall construction resulting from sound waves entrained in the gas stream moving through the mufiier.

Another object of the invention includes the formation of a three-element shell or wall construction for a sound attenuating instrumentality wherein an intermediate element is formed with spaced rectilinear ridges or lands engageable with the other elements of the shell construction to establish a series of gas containing chambers which, together with the reinforcement provided through the engagement of the ridges with the shell Wall elements, function to effectively reduce shell vibration or shell noise.

A further object of the invention resides in a novel method of fabricating and assembling a mufiier having a multi-layer wall construction with end heads or closures applied in a manner to securely retain the wall layers in proper relation for most eflicient sound attenuation and reduction in shell noise.

Further objects and advantages are within the scope of this invention such as relate to the arrangement, operation and function of the related elements of the structure, to various details of construction and to combinations of parts, elements per se, and to economies of manufacture and numerous other features as will be apparent from a consideration of the specification and drawing of a form of the invention, which may be preferred, in which:

Figure 1 is a longitudinal sectional view of a muffier construction embodying my invention;

Figure 2 is a transverse sectional view taken substantially on the line 22 of Figure 1;

Figure 3 is a fragmentary isometric view illustrating one form of multi-layer shell wall construction of the invention;

Figure 4 is a view similar to Figure 3 illustrating another form of multi-layer shell wall construction;

Figure 5 is a sectional view illustrating the shell wall construction of my invention as applied to a cylindrically shaped muffler;

Figure 6 is a fragmentary detail view illustrating a modified arrangement of securing the overlapping ele' ments or layers of a shell Wall together. and

Figure 7 is a fragmentary sectional view illustrating a method of securing the snell wall components together.

While l have illustrated the forms of shell construction of my invention as embodied in a type of mufiier or silencer constructed and arranged especially for attenusting sound waves of an exhaust gas stream from an internal combustion engine, it is to be understood that l contemplate the utilization of the invention for use generally with rapidly moving gas streams for damping or minimizing audible sounds resulting from vibrations of the shell construction.

Figures 1 and 2 illustrate a mutller construction embodying a form of my invention of multilayer or multiwall shell formation. The shell construction it? is formed with an outer shell or wall 11, an inner shell or wall 12 and an intermediate layer, element or member 14. The walls 11 and 12 and the member id may be fashioned or configurated to any form and, as shown in Figures 1 and 2, are generally of elliptical or oval configuration in radially spaced, telescoping relation. The walls or wall members 11 and 12 and the intermediate member 1-1 are fashioned as independent sheets of metal such, for example, as steel, are coextensively assembled and may be joined together by an overlapping seam configuration, one form of which is illustrated at 16.

The muttler shell construction is provided at its ends with heads or end closures 17 and 18, each of which is formed with peripheral flange configuration of U-shaped cross-section as shown at 20, which are adapted to embrace the extremities of the inner and outer walls 11 and 12 which have been drawn or fashioned into juxtaposed position at their extremities to form a sealed juncture between the wall construction and the end heads. The intermediate member or sheet of metal 14 preferably terminates at the juncture of the inner and outer walls as shown in Figure 1, but, if desired, it may be projected between the walls 11 and 12 and also embraced within the U-shaped configurations of the end heads as shown in Figure 7.

The member 14 is preferably formed of undulated, corrugated or wave-like configuration as illustrated in Figures 2 and 3 and presents two series of ridges or rectilinear zones 22 and 24 which respectively engage the inner surface of the outer wall 11 and the outer wall surface of the inner wall 12 as illustrated in Figures 2 and 3. The ridges 22 engaging the outer wall 11 form therewith successive chambers or compartments 26 while the ridges 24- engaging the inner wall 12 form therewith chambers r comparements 28. The chambers of each of the series 26 and 28 are substantially independent and isolated one from another forming air cushions or chambers which serve to dampen vibrations of the shell wall components during the passage of sound entrained streams of gases through the mufiler. In the construction shown in Figure 1, the ends of the intermediate member 14 terminating adjacent the juncture of the inner and outer walls may not establish an air-tight seal between adjacent chambers as some clearance is provided but is of such minute size that it does not materially interfere with the cushioning or damping effect of the substantially independent air chambers provided between the intermediate member 14 and the walls 11 and 12. If it is desired to effect a substantially fluid-tight seal between the ends of the intermediate member and the juncture of the inner and outer shell walls, the end portions of the member 14 may be extended and disposed between the termini of the shell walls and embraced within the U-shaped flange formation as shown in Figure 7.

The mufller construction is formed with a gas inlet passage 32 provided by a tube 33 extending through an opening formed in an end head 17, being welded or otherwise secured to a flange 34 formed on the end head and bounding the opening accommodating the tube 33. The tube 33 is telescoped with a tube 35 which conveys the gas stream to an intermediate or central zone of the mufiier. The central zone of the mufller is provided with a pair of longitudinally spaced, transversely extending walls or partitions 37 and 38 forming a combined gas expansion and sound attenuating chamber 39. The interior of the mufiier is also provided with groups of partitions or baflies 4i) and 41 which form resonance or sound attenuating chambers 42, 43, 44, 45, 46 and 47. Each of the partitions or baffles and 41 is provided with openings 48 which provide acoustic couplings between adjacent resonance chambers.

The mufiiler is provided with a gas outlet passage 50 formed by a tube 51 extending through an opening in the end head 18 which is telescoped with a second tube 54 extending into the interior of the muffler. Both the gas inlet tube 35 and the outlet tube 54 extend through openings formed in the walls or partitions 37 and 38. The walls or portions of the gas passage tubes disposed between the transverse walls 37 and 38 are provided with a comparatively large number of small openings or perforations 57 to facilitate the transfer of gas from the inlet passage to the outlet passage and to form acoustic couplings with the chamber 39 whereby the latter functions as a sound trap chamber for attenuating sound waves entrained in the gas stream. The chambers 44 and 45 also function as gas transfer means to secure adequate flow of exhaust gases through the muffier without setting up excessive back pressure. Positioned intermediate the gas passage tubes 35 and 54 and between the partitions 37 and 38 is a pair of concentrically disposed sleeves or tubes 63 and 61 each formed respectively with a comparatively large number of small openings 62 and 63 which form gas passages and acoustic couplings for attenuating sound waves.

The method of assembling the components of the muffier and especially the casing or shell construction is accomplished in the following manner: The member 14 may be corrugated or undulated by passing a uniplanar metal sheet through suitable corrugating devices. The outer and inner layers 11 and 12 are then assembled in the flat with the intermediate member. The three-element assembly may then be passed through suitable bending devices or rolls to form the assembly into the configuration shown in Figure 2 and the meeting edges of the shell wall elements 11 and 12 interlocked to form the seam 16. If desired, the edges of the intermediate member 14 may also be interlocked with the overlapping portions of the walls 11 and 12. The gas passage tubes and transverse wall members forming the interior construction of the muffler may then be inserted and the end heads 17 and 18 fitted into position. It is preferable to initially form the end heads with the outermost portion 20' of the flange configuration 20 extending angularly outwardly as shown in Figure 7; and, after the end head is in proper position with the extremities of the shell wall construction extending into the U-shaped configuration thereof, the flange portion 20' may be rolled or crimped into binding engagement with the shell Wall elements as shown in Figures 1 and 7 to securely hold the end heads in assembled relation with the shell wall construction.

The muffler functions in the following manner: The exhaust gas stream from an internal combustion engine is directed by a suitable exhaust pipe through the inlet tube 35 and may pass through openings 57 in the side walls of the gas passage tube 35 or through the gas transfer chamber 45 into tube thence laterally through perforations 62, 61 and 57 into the gas outlet tube 54. The gas may also flow in a reverse direction through the tube 60 into the gas transfer chamber 44 thence into the outlet tube 54. During the passage of the gas streams through the mufiler, a large portion of the sound waves entrained therein are attenuated through the arrangement of baffle walls, perforated tubes and resonance chambers.

The movement of the gases through the mufller and T the fact that the muffler is connected by a metal exhaust pipe or tube with the engine sets up vibratory movements of the shell of the muffler which are usually referred to as shell noise. In the present invention the shell noise is substantially eliminated or materially reduced through the utilization of a tubular wall consisting of sheet metal layers 11 and 12 and the intermediate member 14 of undulated configuration which serves to reinforce the walls 11 and 12 in longitudinal zones radially of the mufiier. The wall reinforcing factor provided through the spaced circumferential engagement of the ridges or lands provided by the undulated member 14 and the substantially isolated air spaces 26 and 23 formed between the member 14 and the shell walls 11 and 12 effectively reduce or eliminate the objectionable mufiier shell noise. In the present arrangement this is accomplished without the use of asbestos or fibrous liners or the like.

Figure 4 illustrates a modified configuration of the in termediate member 14 which is fashioned with circumferentially elongated portions or lands and 71 respectively engaging the outer shell wall 11 and the inner shell 12 to reinforce the shells and provide air chambers or compartments 26' and 28'.

Figure 5 is a sectional view illustrative of the arrangement of my invention embodied in a mufiler cylindrically shaped in cross-section. In Figure 5 the inner and outer shells designated 75 and 76 respectively are spaced apart with an intermediate member 77 of undulated configuration disposed therebetween in the manner illustrated in Figure 5, the inner and outer walls and the intermediate member 77 being secured together by a longi tudinal seam indicated at 78 similar to the seam 16 illustrated in Figure 2. I

The space between the inner and outer Walls of the shell construction should be sufficient to accomplish the stated purposes and in practice may be from onesixteenth inch to three-sixteenths inch. it is desirable to utilize a minimum space thickness in the interest of compactness. While the inner and outer walls and the intermediate member may be of suitable thickness, it has been found the metal sheets of from twenty-thousandths inch to forty-thousandths inch are suitable for the purpose.

Figure 6 is illustrative of an alternative means of securing the inner and outer walls and intermediate member together in lieu of the interlocking seam as shown at 16 in Figure 2 and 78 in Figure 5. In this form the inner and outer walls and the intermediate member are arranged in overlapping relation as indicated at 80 and may be spot or tack welded together as at 81. This form of securing the shell wall components and intermediate member together may be advantageously used when the metal sheets used in making the shell walls are of considerable thickness.

It is apparent that, within the scope of the invention, modifications and different arrangements may be made other than is herein disclosed, and the present disclosure is illustrative merely, the invention comprehending all variations thereof.

What I claim is:

l. A nmfilcr for use with the exhaust system of an internal combustion engine including a casing; said casing including a pair of metal sheets formed to tubular shape and disposed in telescoped and spaced relation,

the meeting edges of the metal sheets being in overlapping relation and secured together forming a joint extending longitudinally of the casing; closures secured at the ends of the casing; said closures being respectively provided with tubes forming exhaust gas inlet and outlet passages; and a member disposed between said metal 4 sheets and having portions engaging the metal sheets and forming therewith a plurality of longitudinally extending compartments, said compartments being out of communication with the interior of the casing.

2. A mufiler for use with the exhaust system of an internal combustion engine including a casing; said casing having a multilayer wall including a pair of metal sheets formed to tubular shape and disposed in telescoped and spaced relation, portions of the metal sheets being in overlapping relation and secured together forming a joint extending longitudinally of the casing; closures secured at the ends of the casing and embracing end zones of the sheets to form a closed chamber between the sheets; said closures being respectively provided with ducts forming gas inlet and outlet passages; a metallic member of undulated configuration disposed between said metal sheets, the ridge portions of the member in unsecured engaging relation with the adjacent surfaces of the metal sheets for damping vibrations of the metal sheets of the casing.

3. A silencer for use with a moving gas stream including a tubular shell construction having a pair of spaced imperforate sheet metal walls; a member formed of sheet metal disposed in the space between said walls,

said member being shaped to provide with said walls a plurality of parallel chambers extending longitudinally of the shell; closures formed of sheet metal arranged at the ends of the shell construction; said closures being provided respectively with a gas inlet and outlet tube; a sound attenuating chamber formed within said silencer; gas passage means in said silencer in communication with the sound attenuating chamber, the chambers formed between said sheet metal walls being out of communication with the gas passage means and the sound attenuating chamber.

4. A silencer for a movingv gas stream including, in combination, a tubular shell construction having inner and outer walls formed of imperforate metal sheets arranged in radially spaced relation; a closure for each end of the tubular shell construction; gas inlet and outlet ducts formed respectively in said closures; sound attenuating means formed in the shell; gas passage means disposed in said shell construction for conveying gas through the silencer; a member disposed between the inner and outer walls, said member being formed with spaced ridges whereby alternate ridges respectively engage the inner and outer walis, said member forming with said walls a plurality of air chambers, said air chambers and the reinforcement of the inner and outer walls provided by said member forming means to damp vibratory movements of the shell walls and thereby reduce shell noise, said chambers being out of communication with the interior of the tubular shell construction.

5. Apparatus for attenuating sound in a moving gas stream including, in combination, a tubular shell having a multi-ply wall structure; end heads secured to the shell to form therewith a tubular chamber; gas inlet and outlet ducts formed respectively in said end heads; sound attenuating means formed in said chamber; an intermediate ply of said wall structure being of undulated shape to dispose adjacent plies in spaced relation, the space formed thereby being isolated from the sound attenuating means formed within the shell to provide an air cushion to reduce shell noise.

6. A muffler for use with the exhaust system of an internal combustion engine including a pair of metal sheets formed to tubular configuration, said sheets being in spaced relation throughout the major area thereof, the meeting portions of the metal sheets being bent upon themselves to form a joint extending longitudinally of the mufiler; a sheet metal element of undulated configuration disposed in the space between the metal sheets and terminating adjacent the juncture of the sheets; closures disposed at the end zones of the sheets and having fianged portions embracing the end zones of the sheets to hold the sheets in fixed relation; gas inlet and outlet ducts formed respectively in said closures, said undulated element forming a plurality of compartments, said end closures sealing the space between the sheets out of communication with the interior of the tubular configuration formed by the sheets.

7. A muffier for use with the exhaust system of an internal combustion engine including a pair of sheet metal elements formed to tubular configuration and arranged in telescoped relation, said elements being assembled in radially spaced relation to form a space therebetween; a metal member of corrugated configuration disposed between said elements and intermediate the end zones of the elements, the end zones of said elements being formed into contiguous relation; closures disposed at the ends of the tubular configuration formed by the elements, gas inlet and outlet ducts formed in said closures respectively, each of said closures having a peripheral recess into which extends an end zone of the elements whereby the elements are held in fixed relation, the lands of the corrugated configuration of said member engaging the adjacent surfaces of said elements.

(References on following page) References Cited in the file of this patent UNITED STATES PATENTS Loper June 13, 1911 Guibert June 13, 1916 Schmidt Aug. 6, 1918 Fowles June 21, 1921 Schwager Nov. 23, 1926 Brown Sept. 19, 1933 Compo Apr. 12, 1938 Deremer Mar. 21, 1939 Moss Mar. 24, 1942 

